The $100 Lunchbox Repeater

$6 SMA cables
$26 Abree Antennas 48.8"
$7 SMA adapters (flex glued to case)
$10 Harbor Freight Apache 1800 Case
$30 UV-5Rs
$21 K1 repeater adapter

This is the base minimum you need to make a repeater box. You could even save $20 on the batteries. You really don't even need the case and SMA bits if you just want to make a central repeater for group use. Granted, some of these were discounted due to Black Friday and Cyber Monday sales. The following are the optional parts that I included in the kit.

$30 Mophie 20Ah batteries (Used/LikeNew on Amazon)
$12 Locks & cable from Harbor Freight
$7~ various chokes (you only need 2. I just have a bunch as cable management)